Floating drilling platform with quick disconnect legs

ABSTRACT

A quick disconnect structural joint for sectioned legs of a self-elevating mobile offshore drilling platform.

United States Patent 11 1 Koop, Jr. et al.

[1 1 3,844,127 Oct. 29, 1974 FLOATING DRILLING PLATFORM WITH QUICK DISCONNECT LEGS Inventors: Francis D. Koop, Jr.; John F.

Woods; Kenneth J. Farmer; Wayne D. Harbin, all of Houston, Tex.

Assignee: Marathon Manufacturing Company,

Houston, Tex.

Filed: May 9, 1973 Appl. No.: 358,670

US. Cl 61/465, 285/90, 285/141, 285/308, 403/165, 403/317, 403/355, 403/378 Int. Cl. E02b 17/00, F161 21/00, F161 35/00 Field of Search 61/465, 53; 285/141, 308,

References Cited UNITED STATES PATENTS 10/1967 Hanes et al 285/90 X 7/1969 Hanes 285/141 12/1971 Moore et al. 61/465 Primary Examiner.lacob Shapiro Attorney, Agent, or FirmPravel & Wilson ABSTRACT A quick disconnect structural ,joint for sectioned legs of a self-elevating mobile offshore drilling platform.

19 Claims, 4 Drawing Figures BACKGROUND OF THE INVENTION The field of this invention is that of self-elevating mobile offshore drilling platforms having sectioned legs with structural joints that can be quickly connected or disconnected.

The exploration for petroleum deposits in offshore land submergedby water has brought about the development of floating drilling platforms, either selfpropelled or towed, so that expensive, massive equipment can be moved from one location to another in a minimum of time. Generally, these drilling platforms, or ships, include legs which can be lowered to the bottom of the submerged land to elevate and support the drilling platform during drilling and can be raised from the bottom while the platform is floated to another location. As exploration has moved to deeper and deeper water these legs, of course, have become longer and today often are 300 feet or more in length. The longer legs when in the raised position have raised the center of gravity of the structure to such an extent that there is a danger of capsizing or overturning the whole platform, especially in rougher water when moving the drilling platform. Hence it has become necessary to remove an upper section or sections of each leg from the section of leg therebelow so that the length of the legs extending above the deck of the drilling platform is shortened sufficiently during the floating of the platform from location to location, to prevent capsizing or instability of the platform.

Such separation ofthe leg sections may obviously be accomplished in various ways, such as by a releasable connecting joint for each leg, an example of which is shown in US. Pat. No. 3,628,336.

It is an object of this invention to provide a new and improved quick disconnect structural joint for each leg of a floating drilling platform having legs with removable sections, wherein the joint which, when connected, distributes. the vertical and lateral loads thereon to prevent damage to the connecting components of the joint and to facilitate separation and con nection of the joints.

SUMMARY OF THE INVENTION The present invention relates to a new and improved quick disconnect structural joint for a drilling platform having sectioned legs, wherein all of the vertical and lateral loads on the joint are distributed to and taken by the male and female joint members rather than the weaker connecting elements of the joint, except for the relatively small vertical forces exerted on the connecting elements when moving the legs upwardly relative to the platform. Additionally, the joint is more readily separable and connectable than prior known joints which is important in view of the magnitude of the legs and each joint and the consequent handling difficulties.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic diagram showing the drilling platform with its legs lowered in the operating or working position;

FIG. 2 is a schematic diagram of one corner of the said drilling platform showing one leg raised and the removable section shown in broken lines;

FIG. 3 is a vertical section of the pin and box joint of this invention; and

FIG. 4 is a sectional view taken across one of the joints of the leg along line 4-4 in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The floating drilling platform 10 carries a plurality of legs 12 which are adapted to be raised and lowered through the drilling platform 10 by a suitable jacking means (not shown). The legs 12 generally have a base 13 which contacts the land underneath the water, or bottom B, and supports the platform 10 above the surface of the water W when the platform 10 is in its working position.

With the exception of the derrick 14 the usual drilling apparatus carried on the drilling platform is not shown and is not a part of the described invention. Each of the legs 12 is generally an open truss structure having three or four substantially vertically disposed tubular members 16, each of which carries a conventional rack 18 for moving each leg 12 up and down through openings in the drilling platform 10. While three legs 12 are preferred, the floating drilling platform 10 may have four or more legs 12 without departing from the scope of this invention. In the present invention, each tubular member 16 is formed with at least one upper releasable detachable section 16a joined to a lower section 16b by a quick disconnect joint J shown in detail in FIGS. 3 and 4.

Where each open truss leg 12 has more than one tubular member 16, the tubular members are connected to form the open truss structure horizontal members 28, diagonal supports 30 and, in the case where a four cornered leg is contemplated, horizontal diagonal members 32, to join tubular members 16 in opposite corners of the leg 12.

The joint I for each leg 12 is preferably identical and therefore only one joint I will be described in detail. Thus, each joint J is comprised of a pin or male member 20 and a box or female member 22 so adapted that in its locked position the annular shoulder 24 of the pin or male member 20 rests with the upper leg section 16a on the circular end surface 26 of the female member 22 to carry the compression forces exerted when the leg 12 is resting on the bottom B supporting the drilling platform 10 in its working position as shown in FIG. I. The female connector 22 has on its interior surface two longitudinally displaced annular surfaces 22a and 22b of a smaller diameter than the bore 220, and with the diameter at the surface 22b being less than at the surface 22a for a purpose to be hereinafter explained. These annular surfaces 22a and 22b are narrow or short in length with respect to the overall length of the joint .I. For example, in a joint .I having an overall length of about 5 feet, the length of each of the annular surfaces 22a and 22b is preferably only 2 to 3 inches and each is positioned such that they register with mating raised surfaces 20a and 20b on the external surface 200 of the male member 20 of the joint .I. The upper annular surface 22a is preferably located near the open end of the female member. Below, and preferably adjacent, the lowermost annular raised surface 22b is a groove 22d, preferably annular, in the female member 22 which carries identical locking segments 34, 36 and 38 and wedge guides 40 positioned to restrain any lateral movement of the locking segments 34, 36 and 38, as will be more fully explained.

The male member 20 of the joint has an annular groove 20d which, when the leg is connected, registers, or mates, with the groove 22d. The annular groove 20d of the male member receives the locking segments 34, 36 and 38 carried in the annular groove 22d of the female member when the joint is made and placed in its locked position, as will be more evident hereinafter.

It is an advantageous feature of this invention that when the joint J is connected, the annular surfaces 20a and 20b on the external surface of the male member 20 bear against the annular surfaces 220 and 22b, respectively, so that any lateral forces acting on each leg 12 caused by water and/or wind against the drilling platform or legs 12 are distributed on these surfaces so as to span substantially the full length of the joint J to prevent a concentration of such forces on any one portion of the joint. When the joint J is in its connected position, it is sealed against the invasion of water into the joint by an O-ring 54 or other suitable seal, preferably located in an annular groove 26a on the upper surface 26 of the female member 22 of the joint.

Turning now to FIG. 4, for illustration purposes, locking segment 34 is shown in its locked position and locking segment 36 is shown completely withdrawn, or stated differently, in its unlocked position. Locking segment 38 is shown in an intermediate position being withdrawn from the annular groove d in the male member 20 by a shaft 56 operated by any suitable power means (not shown). Locking segment 34 is shown being held in its locked position by a locking pin 58 which is inserted through a hole 60 through the female member 22 communicating with the annular groove 22d. At least part of said hole 60 is threaded to secure the pin 58 to hold the locking segment 34 in position. When the joint J is connected for normal usage, each such locking segment 34, 36 and 38 is held in the locked position shown for the segment 34 by an identical or a similar pin 58. The hole 60 is made water tight when the joint is connected and locked by an O-ring 62 which may be conveniently carried on the pin 58 which has external threads 58a to mate with the internal threads of the hole 60.

Each locking segment 34, 36 and 38 has a threaded opening 52 in alignment with the hole 60 to receive the pin 58 when in the locking position and the shaft 56 of the tool to remove the locking segment from the annular groove 20d. The internal threads of the hole 52 register with the external threads of the tool shaft 56 so that the shaft 56 is attached to each locking segment 34, 36 and 38 in the manner shown in FIG. 4 for the locking segment 38 to withdraw each segment from the groove 20d and into the groove 22d, or to insert each segment from the groove 20d to the locking position spanning both of the grooves 20d, 22d.

Locking segment 36 is shown being held in an unlocked position by a lock-out bolt 64 in one of the holes 60, which bolt 64 has inner threads registering with the threads of the hole 52 in the locking segment 36 and outer threads in threaded engagement with threads in the hole 60. Each segment may be similarly locked in the retracted position so as to be completely out of the groove 20d when the joint is to be separated and assembled. The lateral extent of each of the locking segments 34, 36 and 38 is such that, when in the locked position, each extends into both grooves 22d and 20d.

The vertical height of each segment 34, 36, 38 is less than the vertical height of the groove 20d so that the upper surface of each segment, such as the upper surface 34a of the segment 34 as shown in FIG. 3 is spaced below the upper surface 20e of the groove 20d. By reason of such construction, vertical downward or compression loads on each leg cannot be transmitted to the segments 34, 36, 38 which are relatively weak structurally as compared to the tubular sections 16a, 16b, and instead, such loads are taken by the legs themselves by the supporting contact at the annular surfaces 24 and 26. Such segments 34, 36, 38 are thus subjected only to vertical upward or tension forces when the legs 12 are being raised relative to the platform 10, and such loads are far less than the compression loads so that they can be adequately handled by such segments without distortion or damage thereto. By preventing the compression loads from being applied to the segments 34, 36, 38, the risk of distorting or even shearing same is avoided, which thereby avoids the risk of such segments being difficult or impossible to retract when it is necessary to disconnect the joint J.

The locking segments 34, 36 and 38 are guided and restrained from lateral movement by wedge guides 40 carried in the groove 22d and affixed to the female member 22 by any suitable means such as pins 66, inserted in holes 72 drilledthrough the female member communicating with the annular groove 22d. The pins 66 may be suitably affixed to female member 22 by welding said pins into said holes 72.

It will be appreciated that the wedge guides 40 could be formed integrally with the member 22, so that the groove 22d is actually segmentally formed to provide a slot 22' for each of the segments 34, 36, 38. The wedge guides 40 have surfaces 40a and 40b facing locking segment 38 (for illustrative purposes) which face, and are substantially parallel to, each other and disposed in the direction of movement of the locking segment 38 to prevent lateral movement of locking segment 38 while said segment 38 moves into, and out of, groove 20d by contact with surfaces 38a and 38b on locking segment 38.

In the operation or use of the joint J of this invention prior to connection, the locking segments 34, 36 and 38 are locked in the withdrawn position in the groove 22d and are so held by the locking bolts 64 as shown in FIG. 4 for the segment 36. The male member 20 is inserted into the female member 22 until the shoulder 24 of said male member 20 bears upon the circular end 26 of the female member 22 and is carried and supported thereupon. In this position, the annular surfaces 20a and 20b of the male member 20 register with, and bear upon, the annular surfaces 22a and 22b, respectively, of the female member 22. The edges of these surfaces are preferably bevelled to allow unobstructed passage of the male member into the assembled position within the female member.

Once the male member 20 has been seated in the female member 22, the lock-out bolts 64 are removed and the locking segments 34, 36 and 38 are moved by suitable power means on the shafts 56 into the annular groove 22a of the male member 22. Then, the shafts 56 are removed from the segments 34, 36, 38 and the locking pins 58 are inserted through the holes 60 and into the holes 52 without threading therein, but with the threads 58a engaging the threads in the holes 60, thus locking the male member 20 within the female member'22.

A particular advantage to the practice of the described invention occurs when the sections of the leg 12 are being removed after the drilling platform has ceased operations at one location and is to be moved to another. The legs 12 are brought up through the drilling platform 10 by the jacking means until the joint is raised to a position where workmen have access thereto. The locking pins 58 are removed and the shaft 56 of a suitable power source are inserted into the holes 60 and screwed into the threads in holes 52 in the segments 34, 36, 38 such as shown for segment 38. The suitable power means then withdraws each segment 34, 36, 38 from its locked position in grooves d and 22d into its unlocked position in groove 22d of the female member 22. Each segment is then locked into the groove 22d with a lockout bolt 64 as shown for segment 36. At this point another particular advantage of this invention comes into play since the only surfaces where substantial contact between the male member 20 and the female member 22 are where annular surface 22a bears upon annular surface 20a and annular surface 22b bears upon annular surface 20b. The male member 20 need be moved only a short vertical distance relative to the female member 22 before the joint J is freed and easily disconnected. Thisis particularly true when the diameter of the surfaces 20b, 22b is less than the diameter of the surfaces 200, 220, since after the disengagement of the surfaces 20a, 22a, the other surfaces of the male member 20 are of a smaller diameter and therefore do not provide any frictional resistance to the separation of the member 20, 22. This advantage is not present in pin and box joints where a substantial amount of the surface of the male member bears against the female member since often, after extended periods of time operating in a single location, a joint becomes bound by either corrosion or the adverse effect of forces applied on said joint. Such joints often require extended periods of time and effort for disconnection to be accomplished. Such disadvantage is not present when the joint of this invention is used.

A further advantage over such prior art joints made possible by the above-described joint .l which contributes to its quick-disconnect properties is that the joint while connected can be lubricated by filling the female member 22 with a suitable lubricant, such as a heavy oil or grease, which is contained by a solid diaphram70 welded to the internal surface 22f of the female member 22 below the joint 1. When the male member 20 is seated in the female member 22 the lubricant fills the open spaces, such as, for example, the annular space between surfaces 20c and 220 and the grooves 22d and 20d, in the joint J. This serves to further protect the joint from corrosion and aids in the disconnection of the joint.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size shape and materials as well as in the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.

We claim:

thereto and each leg having a tubular member, power means for raising and lowering said leg relative to said platform, and said leg including a removable upper section and a joint for connecting the removable section to the remaining portion of said leg; the improvement residing in said joint, comprising:

a female member having a plurality of longitudinally displaced raised annular surfaces,

a male member adapted to be received by said female member having a plurality of longitudinally displaced raised annular surfaces which mate with, and bear against, the corresponding raised annular surfaces of the female member, said raised annular surfaces being narrow with respect to the longitudinal length of the joint; and

locking means for releasably locking said male and female members together.

2. The structure of claim 1, wherein said floating drilling platform includes:

a plurality of open truss legs having a plurality of tubular members at the corners of said legs.

3. The structure of claim 2, wherein said raised annular surfaces of said female member of said joint are longitudinally displaced such that the one such annular surface is near the open end of said female member.

4. The structure of claim 3, wherein there are two longitudinally displaced raised annular surfaces.

5. The structure of claim 4, wherein:

said male and female members having opposing annular grooves which are aligned with each other with said male member inserted in said female member, said locking means being mounted with said annular groove in said female member; and

said other such annular surface is adjacent said annular groove in said female member.

6. in an offshore drilling platform comprising a floating drilling platform, a plurality of legs mounted with 1. In an offshore drilling platform comprising a floating drilling platform, a plurality of legs mounted with said platform for longitudinal movement relative said platform for longitudinal movement relative thereto and each leg having a tubular member, power means for raising and lowering said leg relative to said platform, and said leg including a removable upper section and a joint for connecting the removable section to the remaining portion of said leg; the improvement residing in said joint, comprising:

a female member having a plurality of internal slots formed therein;

a male member adapted to be received by said female member and having an annular groove with nontapered faces adapted to be laterally aligned with said slots;

a segmented locking element in each of said slots;

means mounting said locking elements for lateral movement from a retracted joint-releasing position in said slots to a locking position spanning said slots and said annular groove;

said male and female members having adjacent flat annular shoulders in abutting contact for transmitting compression loads from said upper removable section to said remaining leg portion therebelow, said flat annular shoulders being positioned to allow said locking elements to be freely moved into said male member annular groove with said nontapered faces; and

the upper surface of each of said locking elements being longitudinally spaced below the supper surface of said annular groove when said shoulders are in abutting contact for thereby assuring that the compression loading on said leg is not taken by said locking segments.

7. The structure set forth in claim 6, including:

guide means between each of said segmental locking elements for guiding same for movement laterally to and from the retracted and locking positions.

8. The structure set forth in claim 7, wherein:

each of said guide means has guide surfaces thereon in engagement with corresponding surfaces on each of said locking elements, and with the surfaces of each locking element being substantially parallel and disposed in the direction of movement of each element when moving to and from the retracted and locking positions.

9. The structure set forth in claim 6, including:

said female member having a lateral opening for each of saidlocking elements; and

a lock-in pin adapted to extend through each said opening for engagement with each said element and having means for securing same to said female member for holding each said locking element in the locking position.

10. The structure set forth in claim 9, including:

seal means between each lock-in pin and said tubular member for preventing fluid from leaking into said joint through said openings.

11. The structure set forth in claim 6, including: said female member having a lateral opening for each of said locking elements; and

a lock-out pin adapted to extend through each said opening and having means for securing same to each said locking element aligned therewith and said female member for holding each said locking element in the retracted position.

12. The structure set forth in claim 6, including:

seal means between said abutting shoulders to prevent fluid from leaking into said joint therebe-- tween.

13. The structure set forth in claim 9, including:

seal means between said abutting shoulders to prevent fluid from leaking into said joint therebetween.

14. The structure set forth in claim 6, wherein:

said female member and said male member have inner and outer longitudinally spaced contacting surfaces, each of a relatively short length as compared to the length of said joint.

15. The structure set forth in claim 14, wherein:

the inner contacting surfaces have a smaller diameter than the outer contacting surfaces to facilitate quick disconnecting of the joint.

16. The structure set forth in claim 6, including:

a solid diaphram attached to the inner surface of the female member below said joint to contain a lubricant in said joint.

17. The structure set forth in claim 15, including:

a solid diaphram attached to the inner surface of the female member below said joint to contain a lubricant in said joint.

18. In an offshore drilling platform comprising a floating drilling platform, a plurality of legs mounted with said platform for longitudinal movement relative thereto and each leg having a tubular member, power means for raising and lowering said leg relative to said platform, and said leg including a removable upper section and a joint for connecting the removable section to the remaining portion of said leg the improvement residing in said joint, comprising:

a female member having a internal, substantially annular groove formed therein;

a male member adapted to be received by said female member and having an annular groove adapted to be laterally aligned with said annular groove in said female member;

segmented locking elements in disposed said annular groove in said female member;

means mounting said locking elements for lateral movement from a retracted joint-releasing position in said slots to a locking position spanning said annular groove in said female member and said annular groove in said male member; and

guide means positioned in said annular groove in said female member between said segmented locking elements for guiding said locking elements for movement laterally to and from said retracting and locking positions.

19. The structure set forth in claim 18, including:

each of said guide means having guide surfaces parallel to the direction of travel of said locking elements for engaging and guiding said locking elements and for supporting said locking elements against lateral movement.

STATES PATENT OFFICE CERTIFICATE OF CQRREQTION Patent 3,844,127 Dated October 29, 1974 Q Francis D. Koop, Jr.; John F. Woods;

Inventafls) Kenneth J. Farmer; Wayne D. Harbin It is certified that error appears in the above-identified patent and that said Letters Patent are hereby sorrecte d as shown below:

Q In column 6, line 65, delete "supper" and substitute therefor upper In column 8, line 32, delete "in said slots".

glgned and Sealed this second D3) Of September 1975 [SEAL] Arrest:

RUTH C. MASON c. MARSHALL DANN Arresting Officer (mnmissiunur uj'larenrs and Trademarks an Q UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 1 E512? Dated October 9, 97-

Francis D. Koop, Jr. John F. Woods; Inventor(s) Kenneth J. Farmer; Wayne D. Harbin It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 6, line 65, delete "supper" and substitute therefor upper In column 8, line 32, delete "in said slots".

Signed and sealed this th day of April 1975.

(SEAL fattest:

C. MARSHALL DANN RUTH C. 2' 60B Commissioner of Patents attesting Officer and Trademarks FORM P0405, (10-59) USCOMM-DC scan-Pee "-5. GUYINIINT 'IINTlIG OFFICE: 

1. In an offshore drilling platform comprising a floating drilling platform, a plurality of legs mounted with said platform for longitudinal movement relative thereto and each leg having a tubular member, power means for raising and lowering said leg relative to said platform, and said leg including a removable upper section and a joint for connecting the removable section to the remaining portion of said leg; the improvement residing in said joint, comprising: a female member having a plurality of longitudinally displaced raised annular surfaces, a male member adapted to be received by said female member having a plurality of longitudinally displaced raised annular surfaces which mate with, and bear against, the corresponding raised annular surfaces of the female member, said raised annular surfaces being narrow with respect to the longitudinal length of the joint; and locking means for releasably locking said male and female members together.
 2. The structure of claim 1, wherein said floating drilling platform includes: a plurality of open truss legs having a plurality of tubular members at the corners of said legs.
 3. The structure of claim 2, wherein said raised annular surfaces of said female member of said joint are longitudinally displaced such that the one such annular surface is near the open end of said female member.
 4. The structure of claim 3, wherein there are two longitudinally displaced raised annular surfaces.
 5. The structure of claim 4, wherein: said male and female members having opposing annular grooves which are aligned with each other with said male member inserted in said female member, said locking means being mounted with said annular groove in said female member; and said other such annular surface is adjacent said annular groove in said female member.
 6. In an offshore drilling platform comprising a floating drilling platform, a plurality of legs mounted with said platform for longitudinal movement relative thereto and each leg having a tubular member, power means for raising and loWering said leg relative to said platform, and said leg including a removable upper section and a joint for connecting the removable section to the remaining portion of said leg; the improvement residing in said joint, comprising: a female member having a plurality of internal slots formed therein; a male member adapted to be received by said female member and having an annular groove with non-tapered faces adapted to be laterally aligned with said slots; a segmented locking element in each of said slots; means mounting said locking elements for lateral movement from a retracted joint-releasing position in said slots to a locking position spanning said slots and said annular groove; said male and female members having adjacent flat annular shoulders in abutting contact for transmitting compression loads from said upper removable section to said remaining leg portion therebelow, said flat annular shoulders being positioned to allow said locking elements to be freely moved into said male member annular groove with said non-tapered faces; and the upper surface of each of said locking elements being longitudinally spaced below the supper surface of said annular groove when said shoulders are in abutting contact for thereby assuring that the compression loading on said leg is not taken by said locking segments.
 7. The structure set forth in claim 6, including: guide means between each of said segmental locking elements for guiding same for movement laterally to and from the retracted and locking positions.
 8. The structure set forth in claim 7, wherein: each of said guide means has guide surfaces thereon in engagement with corresponding surfaces on each of said locking elements, and with the surfaces of each locking element being substantially parallel and disposed in the direction of movement of each element when moving to and from the retracted and locking positions.
 9. The structure set forth in claim 6, including: said female member having a lateral opening for each of said locking elements; and a lock-in pin adapted to extend through each said opening for engagement with each said element and having means for securing same to said female member for holding each said locking element in the locking position.
 10. The structure set forth in claim 9, including: seal means between each lock-in pin and said tubular member for preventing fluid from leaking into said joint through said openings.
 11. The structure set forth in claim 6, including: said female member having a lateral opening for each of said locking elements; and a lock-out pin adapted to extend through each said opening and having means for securing same to each said locking element aligned therewith and said female member for holding each said locking element in the retracted position.
 12. The structure set forth in claim 6, including: seal means between said abutting shoulders to prevent fluid from leaking into said joint therebetween.
 13. The structure set forth in claim 9, including: seal means between said abutting shoulders to prevent fluid from leaking into said joint therebetween.
 14. The structure set forth in claim 6, wherein: said female member and said male member have inner and outer longitudinally spaced contacting surfaces, each of a relatively short length as compared to the length of said joint.
 15. The structure set forth in claim 14, wherein: the inner contacting surfaces have a smaller diameter than the outer contacting surfaces to facilitate quick disconnecting of the joint.
 16. The structure set forth in claim 6, including: a solid diaphram attached to the inner surface of the female member below said joint to contain a lubricant in said joint.
 17. The structure set forth in claim 15, including: a solid diaphram attached to the inner surface of the female member below said joint to contain a lubricant in said joint.
 18. In an offshore drilling platform comprisinG a floating drilling platform, a plurality of legs mounted with said platform for longitudinal movement relative thereto and each leg having a tubular member, power means for raising and lowering said leg relative to said platform, and said leg including a removable upper section and a joint for connecting the removable section to the remaining portion of said leg the improvement residing in said joint, comprising: a female member having a internal, substantially annular groove formed therein; a male member adapted to be received by said female member and having an annular groove adapted to be laterally aligned with said annular groove in said female member; segmented locking elements in disposed said annular groove in said female member; means mounting said locking elements for lateral movement from a retracted joint-releasing position in said slots to a locking position spanning said annular groove in said female member and said annular groove in said male member; and guide means positioned in said annular groove in said female member between said segmented locking elements for guiding said locking elements for movement laterally to and from said retracting and locking positions.
 19. The structure set forth in claim 18, including: each of said guide means having guide surfaces parallel to the direction of travel of said locking elements for engaging and guiding said locking elements and for supporting said locking elements against lateral movement. 